798 research outputs found
A canonical Frobenius structure
We show that it makes sense to speak of THE Frobenius manifold attached to a
convenient and nondegenerate Laurent polynomialComment: 24 page
On distribution formulas for complex and -adic polylogarithms
We study an -adic Galois analogue of the distribution formulas for
polylogarithms with special emphasis on path dependency and arithmetic
behaviors. As a goal, we obtain a notion of certain universal Kummer-Heisenberg
measures that enable interpolating the -adic polylogarithmic distribution
relations for all degrees.Comment: This article has appeared in the proceedings volume "Periods in
Quantum Field Theory and Arithmetic" (J.~Burgos Gil, K.~Ebrahimi-Fard,
H.~Gangl eds), [Conference proceedings ICMAT-MZV 2014] Springer Proceedings
in Mathematics \& Statistics {\bf 314} (2020), pp.593--61
Fourier-Laplace transform of a variation of polarized complex Hodge structure, II
We show that the limit, by rescaling, of the `new supersymmetric index'
attached to the Fourier-Laplace transform of a polarized variation of Hodge
structure on a punctured affine line is equal to the spectral polynomial
attached to the same object. We also extend the definition by Deligne of a
Hodge filtration on the de Rham cohomology of a exponentially twisted polarized
variation of complex Hodge structure and prove a E_1 degeneration property for
it.Comment: 51 pages, revised version, to appear in the proceedings volume of the
conference `` New developments in Algebraic Geometry, Integrable Systems and
Mirror symmetry", RIMS, Kyoto, Jan. 7-11, 200
Tungsten divertor sources in WEST related to impurity inventory and local plasma conditions
A dedicated series of L-mode deuterium discharges were performed in WEST in which a broad parameter space in terms of divertor plasma temperature (inner divertor at <10 eV, outer divertor up to 50 eV) and impurity flux density was achieved by variation of X point elevation, upstream plasma density and fuelling position and rate. Density steps provided stable reference plasma conditions whilst density scans up to the point of detachment revealed the sputtering threshold behaviour of the dominant sputtering species. Tungsten gross erosion was quantified via the common WI 400.9 nm line and correlated with the residual gas content.</p
The effect of discharge chamber geometry on the ignition of low-pressure rf capacitive discharges
This paper reports measured and calculated breakdown curves in several gases of rf capacitive discharges excited at 13.56 MHz in chambers of three different geometries: parallel plates surrounded by a dielectric cylinder (“symmetric parallel plate”), parallel plates surrounded by a
grounded metallic cylinder (“asymmetric parallel plate”), and parallel plates inside a much larger grounded metallic chamber (“large chamber”). The breakdown curves for the symmetric chamber have a multivalued section at low pressure. For the asymmetric chamber the breakdown curves are shifted to lower pressures and rf voltages, but the multivalued feature is still present. At higher pressures the breakdown voltages are much lower than for the symmetric geometry. For the large chamber geometry the multivalued behavior is not observed. The breakdown curves were also calculated using a numerical model based on fluid equations, giving results that are in satisfactory
agreement with the measurements
ICRH operations and experiments during the JET-ILW tritium and DTE2 campaigns
2021 has culminated with the completion of the JET-ILW DTE2 experimental campaign. This contribution summarizes Ion Cyclotron Resonance Heating (ICRH) operations from system and physics point of view. Improvements to the (ICRH) system, to operation procedures and to real time RF power control were implemented to address specific constraints from tritium and deuterium-tritium operations and increase the system reliability and power availability during D-T pulses. ICRH was operated without the ITER-Like Antenna (ILA) because water leaked from an in-vessel capacitor into the vessel on day-2 of the D-T campaign. Three weeks were required to identify and isolate the leak and resume plasma operations. Dedicated RF-Plasma Wall Interaction (PWI) experiments were conducted; tritium plasmas exhibit a higher level of Be sputtering on the outer wall and impurity content when compared to deuterium or hydrogen plasmas. The JET-DTE2 campaigns provided the opportunity to characterize ICRH schemes foreseen for the ITER operation, in the ITER like wall environment in ELMy H-mode scenarios aiming at maximizing fusion performance. The second harmonic tritium resonance heating and to a lesser extent minority 3He heating (ITER D-T ICRH reference schemes) lead to improved ion temperature and fusion performance when compared to hydrogen minority ICRH. However, these discharges suffered from a lack of stationarity and gradual impurity accumulation potentially because of a deficit of ICRH power when using JET antennas at lower frequencies. Fundamental deuterium ICRH was used in tritium-rich plasmas and with deuterium Neutral Beam Heating; this ICRH scheme proved to be very efficient boosting ion temperature and fusion performance in these plasmas
The effect of discharge chamber geometry on the ignition of low-pressure rf capacitive discharges
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